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            <h2 class="title" style="clear: both"><a id="envevent_notify"></a>DbEnv::set_event_notify()</h2>
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      <pre class="programlisting">#include &lt;db_cxx.h&gt;
 
int
DbEnv::set_event_notify(
    void (*db_event_fcn)(DB_ENV *dbenv, u_int32_t event, 
    void *event_info));</pre>
      <p>
         The <code class="methodname">DbEnv::set_event_notify()</code> method
         configures a callback function which is called to notify the
         process of specific Berkeley DB events.
    </p>
      <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
        <h3 class="title">Note</h3>
        <p>
            Berkeley DB is not re-entrant. Callback functions should
            not attempt to make library calls (for example, to release
            locks or close open handles). Re-entering Berkeley DB is
            not guaranteed to work correctly, and the results are
            undefined.
        </p>
      </div>
      <p>
         The <code class="methodname">DbEnv::set_event_notify()</code> method
         configures operations performed using the specified 
         <a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>  handle, not all operations
         performed on the underlying database environment.
    </p>
      <p>
         The <code class="methodname">DbEnv::set_event_notify()</code> method may
         be called at any time during the life of the application.
    </p>
      <p>
         The <code class="methodname">DbEnv::set_event_notify()</code> <span>
            
            <span>
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            </span>
        </span>
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp7249024"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp7244960"></a>db_event_fcn</h4>
              </div>
            </div>
          </div>
          <p>
                The <span class="bold"><strong>db_event_fcn</strong></span> parameter is the
                application's event notification function.  The function takes three
                parameters:
            </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p>
                        <code class="literal">dbenv</code>
                    </p>
                <p>
                        The <span class="bold"><strong>dbenv</strong></span>
                        parameter is the enclosing database environment
                        handle.
                    </p>
              </li>
              <li>
                <p>
                        <code class="literal">event</code>
                    </p>
                <p>
                        The <span class="bold"><strong>event</strong></span> parameter is one of the
                        following values:
                    </p>
                <div class="itemizedlist">
                  <ul type="circle">
                    <li>
                      <p><a id="event_notify_DB_EVENT_PANIC"></a>
                                <code class="literal">DB_EVENT_PANIC</code>
                           </p>
                      <p>
                                Errors can occur in the Berkeley DB library where the only solution
                                is to shut down the application and run recovery (for example, if
                                Berkeley DB is unable to allocate heap memory).  In such cases, the
                                Berkeley DB methods will return 
                                <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.
                                It is often easier to simply exit the application when such errors
                                occur rather than gracefully return up the stack.
                           </p>
                      <p>
                               When <span class="bold"><strong>event</strong></span> is set to
                               <code class="literal">DB_EVENT_PANIC</code>, the database environment has
                               failed.  All threads of control in the database environment should
                               exit the environment, and recovery should be run.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REG_ALIVE"></a>
                                <code class="literal">DB_EVENT_REG_ALIVE</code>
                            </p>
                      <p>
                                Recovery is needed in an environment where the 
                                <a class="link" href="envopen.html#envopen_DB_REGISTER">DB_REGISTER</a> 
                                flag was specified on the 
                                <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method and there is 
                                a process attached to the environment.   The callback function is triggered
                                once for each process attached. 
                            </p>
                      <p>
                                The <span class="bold"><strong>event_info</strong></span> parameter points to a pid_t value 
                                containing the process identifier (pid) of the process the Berkeley DB library
                                detects is attached to the environment.   
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REG_PANIC"></a>
                                <code class="literal">DB_EVENT_REG_PANIC</code>
                            </p>
                      <p>
                                Recovery is needed in an environment where the
                                <a class="link" href="envopen.html#envopen_DB_REGISTER">DB_REGISTER</a>
                                flag was specified 
                                on the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method.  All threads
                                of control in the database environment should exit the environment.   
                            </p>
                      <p>
                                This event is different than the <code class="literal">DB_EVENT_PANIC</code> event
                                because it can only be triggered when <code class="literal">DB_REGISTER</code> was
                                specified.   It can be used to distinguish between the case when a process
                                dies in the environment and recovery is initiated versus the case when an
                                error happened (for example, if Berkeley DB is unable to allocate heap
                                memory)
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_CLIENT"></a>
                                <code class="literal">DB_EVENT_REP_CLIENT</code>
                            </p>
                      <p>
                                The local site is now a replication client.
                            </p>
                      <p>
                                This event is generated when the replication role changes to client,
                                either from master or from being unset. The role is unset when an
                                environment is first created and after an environment is recovered.
                                This event is not generated when restarting replication in an
                                environment that was previously a client and was opened without
                                recovery.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_CONNECT_BROKEN"></a>
                               <code class="literal">DB_EVENT_REP_CONNECT_BROKEN</code>
                            </p>
                      <p>
                                A previously established replication message connection between the
                                local site and a remote site has been broken. This event supplies
                                the EID of the remote site, and an integer error code that
                                identifies the reason the connection was broken.
                            </p>
                      <p>
                                A non-zero error code indicates an unexpected
                                condition such as a hardware failure or a
                                protocol error.  An application might respond
                                by emitting an informational message or passing
                                this information to other parts of the
                                application using the
                                <code class="literal">app_private</code>
                                field.  A zero error code indicates that the
                                connection was cleanly closed by the other end.
                                Replication Manager retries broken connections
                                periodically until they are restored.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_CONNECT_ESTD"></a>
                               <code class="literal">DB_EVENT_REP_CONNECT_ESTD</code>
                            </p>
                      <p>
                                A replication message connection has been established between the
                                local site and a remote site. This event supplied the EID of the
                                remote site.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_CONNECT_TRY_FAILED"></a>
                               <code class="literal">DB_EVENT_REP_CONNECT_TRY_FAILED</code>
                            </p>
                      <p>
                                An attempt to establish a connection between the local site and a
                                remote site has failed. This event supplies the EID of the remote
                                site, and an integer error code that identifies the reason the
                                connection attempt failed.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_DUPMASTER"></a>
                            <code class="literal">DB_EVENT_REP_DUPMASTER</code>
                            </p>
                      <p>
                                Replication Manager has detected a duplicate master situation, and
                                has changed the local site to the client role as a result.  If the 
                                <a class="link" href="repconfig.html#config_DB_REPMGR_CONF_ELECTIONS">DB_REPMGR_CONF_ELECTIONS</a>
                                configuration parameter has been turned off, the application should
                                now choose and assign the correct master site.  If
                                <code class="literal">DB_REPMGR_CONF_ELECTIONS</code> is turned on, the
                                application may ignore this event.
                            </p>
                      <p>
                                The <code class="literal">DB_EVENT_REP_DUPMASTER</code> event is provided 
                                only to applications configured for the replication manager.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_ELECTED"></a>
                                <code class="literal">DB_EVENT_REP_ELECTED</code>
                            </p>
                      <p>
                                The local replication site has just won an election.  An application
                                using the Base replication API should arrange for a call to the 
                                <a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a>  method
                                after receiving this event, to reconfigure the local environment as a
                                replication master.
                            </p>
                      <p>
                                Replication Manager applications may safely ignore this event.  The
                                Replication Manager calls <a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a> 
                                automatically on behalf of the application when appropriate (resulting
                                in firing of the DB_EVENT_REP_MASTER event).
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_ELECTION_FAILED"></a>
                            <code class="literal">DB_EVENT_REP_ELECTION_FAILED</code>
                            </p>
                      <p>
                                Replication Manager tried to run an election to choose a master
                                site, but the election failed due to lack of timely participation by
                                a sufficient number of other sites.  Replication Manager will
                                automatically retry the election later.  This event is for
                                information only.
                            </p>
                      <p>
                                The <code class="literal">DB_EVENT_REP_ELECTION_FAILED</code> event is
                                provided only to applications configured for the replication
                                manager.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_ELECTION_STARTED"></a>
                            <code class="literal">DB_EVENT_REP_ELECTION_STARTED</code>
                            </p>
                      <p>
                                Replication Manager has started an election
                                to choose a master site.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_INIT_DONE"></a>
                               <code class="literal">DB_EVENT_REP_INIT_DONE</code>
                            </p>
                      <p>
                                Replication Manager has completed an
                                internal initialization procedure.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_JOIN_FAILURE"></a>
                               <code class="literal">DB_EVENT_REP_JOIN_FAILURE</code>
                            </p>
                      <p>
                                The local client site is unable to synchronize with a new master,
                                possibly because the client has turned off automatic internal
                                initialization by setting the 
                                <a class="link" href="repconfig.html#config_DB_REP_CONF_AUTOINIT">DB_REP_CONF_AUTOINIT</a>
                                flag to <code class="literal">0</code>.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_LOCAL_SITE_REMOVED"></a>
                               <code class="literal">DB_EVENT_REP_LOCAL_SITE_REMOVED</code>
                            </p>
                      <p>
                                The local site has been
                                removed from the replication group.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_MASTER"></a>
                                <code class="literal">DB_EVENT_REP_MASTER</code>
                            </p>
                      <p>
                                The local site is now the master site of its replication group.  It is
                                the application's responsibility to begin acting as the master
                                environment.
                            </p>
                      <p>
                                This event is generated when the replication role changes to master,
                                either from client or from being unset. The role is unset when an
                                environment is first created and after an environment is recovered.
                                This event is not generated when restarting replication in an
                                environment that was previously a master and was opened without
                                recovery.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_MASTER_FAILURE"></a>
                            <code class="literal">DB_EVENT_REP_MASTER_FAILURE</code>
                            </p>
                      <p>
                                A Replication Manager client site has detected the loss of
                                connection to the master site.  If the 
                                <a class="link" href="repconfig.html#config_DB_REPMGR_CONF_ELECTIONS">DB_REPMGR_CONF_ELECTIONS</a>
                                configuration parameter is turned on, Replication Manager will
                                automatically start an election in order to choose a new master. In
                                this case, this event may be ignored.
                            </p>
                      <p>
                                When <code class="literal">DB_REPMGR_CONF_ELECTIONS</code> is turned off, the
                                application should choose and assign a new master. Failure to do so
                                means that your replication group has no master, and so it cannot
                                service write requests.
                            </p>
                      <p>
                                The <code class="literal">DB_EVENT_REP_MASTER_FAILURE</code> event is provided
                                only to applications configured for the replication manager.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_NEWMASTER"></a>
                            <code class="literal">DB_EVENT_REP_NEWMASTER</code>
                            </p>
                      <p>
                                The replication group of which this site is a member has just
                                established a new master; the local site is not the new master.  The
                                <span class="bold"><strong>event_info</strong></span> parameter points to an
                                integer containing the environment ID of the new master.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_PERM_FAILED"></a>
                                <code class="literal">DB_EVENT_REP_PERM_FAILED</code>
                            </p>
                      <p>
                                The replication manager did not receive enough acknowledgements (based
                                on the acknowledgement policy configured with 
                                <a class="xref" href="repmgrset_ack_policy.html" title="DbEnv::repmgr_set_ack_policy()">DbEnv::repmgr_set_ack_policy()</a> )
                                to ensure a transaction's durability within the replication group. 
                                The transaction will be flushed to the master's local disk storage for
                                durability.
                            </p>
                      <p>
                                The <code class="literal">DB_EVENT_REP_PERM_FAILED</code> event is provided
                                only to applications configured for the replication manager.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_SITE_ADDED"></a>
                               <code class="literal">DB_EVENT_REP_SITE_ADDED</code>
                            </p>
                      <p>
                                A new site has joined the group. 
                                The 
                                <span class="bold"><strong>event_info</strong></span> parameter points to an
                                integer containing the environment ID of the new site.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_SITE_REMOVED"></a>
                               <code class="literal">DB_EVENT_REP_SITE_REMOVED</code>
                            </p>
                      <p>
                                An existing remote site has been removed from the group.  The
                                <span class="bold"><strong>event_info</strong></span> parameter points to an
                                integer containing the environment ID of the site that was removed.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_REP_STARTUPDONE"></a>
                               <code class="literal">DB_EVENT_REP_STARTUPDONE</code>
                            </p>
                      <p>
                               The client has completed startup synchronization and is now processing
                               live log records received from the master.
                            </p>
                    </li>
                    <li>
                      <p><a id="event_notify_DB_EVENT_WRITE_FAILED"></a>
                               <code class="literal">DB_EVENT_WRITE_FAILED</code>
                            </p>
                      <p>
                                A Berkeley DB write to stable storage failed.
                            </p>
                    </li>
                  </ul>
                </div>
              </li>
              <li>
                <p>
                        <code class="literal">event_info</code>
                    </p>
                <p>
                        The <span class="bold"><strong>event_info</strong></span> parameter may
                        reference memory which contains additional information describing an
                        event.  By default, <span class="bold"><strong>event_info</strong></span> is
                        NULL; specific events may pass non-NULL values, in which case the
                        event will also describe the memory's structure.
                    </p>
              </li>
            </ul>
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      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp7269232"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
                <a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>  
            </p>
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      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp7228840"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
                     <a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a> 
                </p>
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